1. Field of the Invention
This invention is directed toward dispersants compatible in lubricating oil. In particular, this invention is directed toward dispersant additives compatible in lubricating oil which are alkylphenyl poly(oxypropylene) aminocarbamates having at least one basic nitrogen and wherein the alkyl group is a substantially straight-chain alkyl group of at least 15 carbon atoms.
The incompatibility of certain dispersant additives in lubricating oil, i.e., oils which contain other additives, is recognized in the art and arises in spite of the fact that certain of these additives are known lubricating oil dispersants.
Several theories exist as to the cause of the lubricating oil incompatibility of certain additives. Without being limited to any theory, it is possible that some of these additives interfere with other additives contained in the lubricating oil and either counterbalance the effectiveness of these additives or actually cause dissolution of one or more of these additives, including possibly the dispersant additive itself. In either case, the incompatibility of the additive with other additives in the lubricating oil demonstrates itself in less than desirable crankcase deposits as measured by Sequence V-D engine tests.
In another theory, it is possible that the additive will decompose in the lubricating during engine operation and the decomposition products are what cause increased crankcase deposits.
It is also possible that the incompatibility of the additive is related to its oil solubility. Lubricating oil incompatible additives are less than desirable insofar as their use during engine operation will result in increased deposits in the crankcase. This problem can be severe. For example, hydrocarbyl poly(oxyalkylene) aminocarbamate, including the hydrocarbyl poly(oxybutylene) aminocarbamate, are known to possess dispersant properties in lubricating oil. In this regard, it is recognized that the hydrocarbyl poly(oxybutylene) aminocarbamates are substantially more expensive than the hydrocarbyl poly(oxypropylene) aminocarbamates. However, because heretofore no known hydrocarbyl poly(oxypropylene) aminocarbamate was found to be sufficiently lubricating oil compatible, it is necessary to employ the more expensive hydrocarbyl poly(oxybutylene) aminocarbamates which are sufficiently lubricating oil compatible. Accordingly, it would be particularly advantageous to develop a hydrocarbyl poly(oxypropylene) aminocarbamate which is compatible in lubricating oil compositions.
The instant invention is directed to a novel class of hydrocarbyl poly(oxypropylene) aminocarbamates which are compatible with the lubricating oil composition. The novel additives of this invention are alkylphenyl poly(oxypropylene) aminocarbamates having a molecular weight of about 600 to 6,000 wherein the alkyl group is substantially straight chain containing at least 15 carbon atoms.
2. Prior Art
Numerous references disclose hydrocarbyl poly(oxyalkylene) aminocarbamates as fuel additives. These include the following U.S. Pat. Nos.:
4,160,648; PA0 4,191,537; PA0 4,197,409; PA0 4,236,020; PA0 4,243,798; PA0 4,270,930; PA0 4,274,837; PA0 4,288,612; PA0 4,521,610; and PA0 4,568,358
Of particular relevance is U.S. Pat. No. 4,274,837 which discloses that hydrocarbyl poly(oxyalkylene) aminocarbamates containing certain poly(oxyalkylene) chains, i.e., oxypropylene, when used in fuels employed in combination with certain lubricating oils, produce crankcase varnish. This reference further discloses that lubricating oil compatible hydrocarbyl poly(oxypropylene) aminocarbamates are improved by employing the poly(oxypropylene) as a block copolymer having 1 to 5 C.sub.9 to C.sub.30 oxyalkylene units.
U.S. Pat. No. 4,160,648 discloses an intake system deposit control additive for fuels which is a hydrocarbyl poly(oxyalkylene) aminocarbamate wherein the hydrocarbyl group is from 1 to 30 carbon atoms including alkyl or alkylphenyl groups. Specifically disclosed hydrocarbyl groups include tetrapropenylphenyl, olelyl and a mixture of C.sub.16, C.sub.18 and C.sub.20 alkyl groups. Likewise U.S. Pat. No. 4,288,612 discloses deposit control additives for gasoline engines which are hydrocarbyl poly(oxyalkylene) aminocarbamates wherein the hydrocarbyl group contains from 1 to about 30 carbon atoms including alkylphenyl groups wherein the alkyl group is straight or branched chain of from 1 to about 24 carbon atoms. U.S. Pat. No. 4,568,358 discloses diesel fuel compositions containing an additive such as a hydrocarbyl poly(oxyalkylene) aminocarbamate. This reference discloses hydrocarbyl groups such as alkyl groups of 1 to 30 carbon atoms; aryl groups of 6 to 30 carbon atoms, alkaryl groups of 7 to 30 carbon atoms, etc.
U.S. Pat. No. 4,332,595 discloses hydrocarbyl poly(oxyalkylene) polyamines wherein the hydrocarbyl group is a hydrocarbyl radical of 8 to 18 carbon atoms derived from linear primary alcohols.
U.S. Pat. Nos. 4,233,168 and 4,329,240 among others disclose lubricating oil compositions containing a dispersant amount of a hydrocarbyl poly(oxyalkylene) aminocarbamate.
While these prior art references disclose C.sub.1 to C.sub.30 hydrocarbyl poly(oxyalkylene) aminocarbamates which include the poly(oxypropylene) polymers, none of these references disclose the unique hydrocarbyl group of this invention nor do any of these references suggest that use of this unique hydrocarbyl group would overcome the art recognized problem of lubricating oil incompatibility arising from using the prior art hydrocarbyl poly(oxypropylene) aminocarbamates.